The present invention relates to a shaped part, especially for use as a sliding or journal bearing that can be axially stressed, with the shaped part including a metallic member and a ceramic member that are positively interconnected via thermal treatment.
Adjoined together shaped parts of this type have been known for a long time and are required in many technical fields, in order, for example, to be able to be used as sliding or journal bearings that can be axially stressed where high process temperatures occur. Typical applications include, for example, pumps or mixers in so-called bioreactors, or pumps in the chemical industry that must operate without leaking at high process temperatures and high temperature gradients. In order to be able to positively or frictionally connect the metallic member with the ceramic member, the two members are first thermally treated, whereby the ceramic member is then generally in the thermally treated state inserted into a corresponding recess opening formed in the metallic member. The two joined-together members are subsequently subjected to a cooling process, whereby the members contract by a predetermined amount so that consequently the metallic member encloses the ceramic member in a positive manner below a prescribed cooling temperature.
However, it is has been shown that as a consequence of high process temperatures at which such members serve, for example, as bearings, the heretofore known bearings can sometimes briefly enter the temperature range in which the positive connection of the two members was effected. The result is a loosening or canceling of the positive connection with a devastating result for the bearing, the consequence generally being a total destruction of the bearing. This serious problem has been attempted to be resolved by providing the ceramic member that is accommodated in the metallic member with mechanical means, for example pins, rings, and/or abutment means in the form of projections or recesses that are formed on the outer contour of the ceramic member and engage in corresponding recesses and projections formed in the metallic member. However, the result of all these measures was that the ceramic member, due to the pressure stresses that inherently acted thereupon in an irregular manner, was increasingly susceptible to a total destruction as a consequence of certain parts failing or breaking off, so that this approach did not provide any significant success.
It is therefore an object of the present invention to provide a shaped part of the aforementioned general type that is sufficiently resistant to high process temperatures, easily maintains its positive connection over a wide temperature range from room temperature to at least 350.degree. C. without any limitation of its function, that its function is similarly maintained at the great temperature gradients that occur in this temperature range, that it can be easily and economically produced, and that no additional measures are required for creating a positive connection between the metallic member and the ceramic member.